Claimed by an Old Enemy
by Takara Phoenix
Summary: Mundie AU - Both Jace and Sebastian had been famous child-actors, their careers really taking off when they co-stared in a TV show together as young teens. Now, ten years later, they reunite on the set for the sequel. Sebastian/Jace slash


Shadowhunters || SebJace || Claimed by an Old Enemy || SebJace || Shadowhunters

Title: Claimed by an Old Enemy – But Shit's Cool I Guess

Fandom: Shadowhunters: The Mortal Instruments

Disclaimer: All rights to the Shadowhunters show reserved to Ed Decter, the books the show is based off and its characters belong to Cassandra Clare. This fanfiction on the other hand is entirely mine. No money is made with this, though reviews are more than welcomed.

Warnings: m/m, mundie actors AU, mutual pining, m/f

Main Pairing: Seb/Jace

Side Pairings: Bat/Maia, Simon/Clary, Luke/Catarina

Shadowhunters Characters: Jonathan Christopher 'Jace' Herondale, Sebastian Verlac | Jonathan Morgenstern, Isabelle Sophia 'Izzy' Lightwood, Clarissa Adele 'Clary' Fray, Simon Lewis, Maia Roberts, Bartholomew 'Bat' Velasquez, Lydia Branwell, Luke Garroway, Catarina Loss, Madzie

Summary: Both Jace and Sebastian had been famous child-actors, their careers really taking off when they co-stared in a TV show together as young teens. Now, ten years later, they reunite on the set for the sequel.

 **Claimed by an Old Enemy**

 _But Shit's Cool I Guess_

"This is amazing! You two look absolutely _amazing_!"

Sebastian heaved a sigh and shook his head. "And you look absolutely ridiculous, Simon."

Simon huffed offended and earned a kiss from his girlfriend. "You're a great Jon Snow."

At that, Simon looked very smug, causing Sebastian to roll his eyes. Honestly, Sebastian had no idea how he had allowed for Clary and Simon to drag him along to Comic Con. Him. He hated those kind of things. But Clary had those puppy-dog eyes, the ones Sebastian just couldn't resist. So here Sebastian was, cosplaying Vision or Vasectomy or whatever the guy was called. The brother of the character Clary was cosplaying as. Dandelion, sister of unicorns, or something. Honestly, Sebastian _really_ , really didn't care. At all. But it put a smile on Clary's face – and that was what really mattered. And Clary looked beautiful in her blue dress, with her white wig with the complicated braids, clinging onto Simon's arm.

"If anyone else recognizes me and asks me for an autograph though, I am leaving for the hotel", threatened Sebastian exhausted. "I swear, I appreciate my fans, but these... Comic Cons always turn into this gigantic nostalgia fest where they look at me with the large, hopeful eyes..."

"Oh my gosh. You're Sebastian Verlac! You're _Octavian_!"

Sebastian made a face and took a deep breath before he turned toward the squeaking fangirl with a charming smile. "The one and only, at least until nostalgia makes them do a reboot."

"They best not!", huffed the fangirl. "That show was the _perfect_ adaptation of _Percy Jackson_!"

Sebastian smiled charmingly as she and her friends asked for a photo. They were in full cosplay as Percy Jackson, Annabeth Chase and Nico di Angelo. With more squeaking did they run off after taking their picture and thanking him profoundly.

"If you'll excuse me, I have to... powder my nose", grunted Sebastian.

"Just don't sneak out on us", ordered Clary with a firm, serious look on her face.

"Wouldn't think of it, sis", chuckled Sebastian as he walked off.

He just needed a breather and the toilet was always his hiding spot, a thing from the past. He had been a big name in his teenage years, but it had been ten years since that. It figured, that the kids who grew up on the show were now, just like him, in their end-twenties and, like most of those, very nostalgic for their childhood. Still, _he_ usually never felt nostalgic for his childhood and the reminders of it usually send spiky-cold showers down his spine.

"Sebastian... Verlac...?"

For a moment, Sebastian made a face before he looked at the person who said his name through the mirror. His eyes widened as recognition also set in on him. Blinking, he turned around.

"Jonathan Wayla... Herondale", whispered Sebastian in disbelief.

"I... I haven't seen you since _Adventures of New Rome_ wrapped up", grunted the other blonde. "Uhm, it's... I go by Jace now. So... how... how have you been since then? Never seen you in any movies or shows or anything since then. You stopped acting, huh?"

"Yeah. Retired", nodded Sebastian. "Saw your latest movie. You were amazing in it."

"Thanks", grinned Jace with the smallest blush, ducking his head. "Hey. A photo?"

"Sure", shrugged Sebastian amused. "There's a lot of _Percy Jackson_ fans out here who already asked me for pictures. They'd probably go nuts seeing a reunion between Jason and Octavian."

Jace grinned as he wrapped an arm around Sebastian's shoulders and took a selfie with him, posting it on twitter with a caption – _Claimed by an old enemy, but shit's cool, I guess #JasonGrace #AdventuresOfNewRome #PjatO #SDCC_

"Well, uhm. Good seeing you again", stated Jace just slightly awkwardly.

"Yeah. You... too", nodded Sebastian and watched Jace go, like a ghost of the past.

/flashback\

Jonathan Wayland and Sebastian Verlac were once famous child-actors, having been formed by _The Circle_ – an agency owned by Valentine Morgenstern. The man groomed orphaned toddlers into becoming child-actors. He raided orphanes and the agents working for him raised the kids, trained them. The biggest child-stars of the early two-thousands had come from _The Circle._

When they barely were teenagers, they met for the first time, co-staring in a TV show. Three years prior, _Percy Jackson and the Olympians_ had started airing on Disney channel, a live-action adaptation of the book-series of the same name about Percy Jackson, a young modern-day Greek hero and son of the god Poseidon. It was such a huge success that they decided to make more money with it by including elements of the sequel book-series, introducing Roman heroes. The spin-off TV show called _Adventures of New Rome_ was born.

For a couple of episodes, Isabelle Lightwood had guest-stared as Reyna on _Percy Jackson_ during season 3. She quickly became a fan-favorite and Disney took the opportunity to spin-off with her, to use her as a back-door pilot into a show centered around he Romans, with her as the female lead. Jonathan Wayland was cast as Jason Grace, the male lead next to Isabelle Lightwood – and the two kids instantly hit it off and became friends.

Isabelle's older brother Alec, while not an actor, was still around the set a lot with their parents, because their mother was Isabelle's agent. And while Jonathan hit it off with Isabelle, he and Alec essentially became best friends. That was how Valentine Morgenstern was revealed to be an abuser who took children and forced them into acting careers, abused them.

Opposite Jonathan and Isabelle played Sebastian Verlac as Octavian, the grumpy kind-of-antagonist who kept sabotaging the two heroes and trying to gain fame for himself. Like Jonathan, Sebastian was also signed on by Morgenstern and had been trained to be the perfect child-actor.

The good thing was that the two boys, and many more, were finally freed from the abuse and found better, safer homes. The bad thing was that both TV shows got canceled before the great crossover. They had just wrapped up the finale for _Percy Jackson and the Olympians_ and fans were anticipating a joined TV show focusing on the sequel series. They didn't want to recast a good junk of their main characters though, so the project got iced. Both TV shows wrapped up with the final battle of the first book-series and that was the end of it, much to the disappointment of the fans.

The police managed to track down Jonathan's biological grandmother to raise him.

Sebastian all the while was reunited with his sister, taken in by her family.

It quieted down around them both as the now former child-actors were made to deal with the trauma they had suffered and finally got to experience what it was like to be a happy child.

/flashback|end\

"Seb, you want a cookie? Sebbie?"

Sebastian blinked a couple of times and shook his head before looking up from the papers he was reading. His two younger sisters were standing in front of him, with flour in their hair and plates of cookies in their hands, grinning like two absolute maniacs. Clary and Madzie. His sisters.

Sometimes, it felt like a whole different life that he was leading once, as Sebastian Verlac. Now, he was Sebastian Garroway. While his birth-mother had been dead already by the time he was freed from Valentine's grasp, her husband had agreed to take Sebastian in so he could grow up with his younger sister Clary. A few years later, Luke Garroway got married to a wonderful and amazing woman – Catarina Loss. And only months later did they adopt Madzie. And now, now Sebastian had a whole, happy, loving family. Luke was a father to him, a proper father who loved and supported him, who gave him advise and guidance when needed. Catarina was a tentative stepmother, but she cared and she always had an open ear for him. And Clary and Madzie – there were no words to describe how much Sebastian loved them.

"You made cookies?", asked Sebastian with a half-smile.

"Ye—es!", exclaimed Madzie proudly and jumped up onto the couch next to him. "Why didn't you _help_? You've been sitting here all afternoon!"

"Sorry. I was... distracted", hummed Sebastian and pushed the papers aside.

Instead, he reached for one of the chocolate cookies. He didn't miss the curious look he got from Clary. She tried to read what he had been reading, but he had covered it well enough for now. He knew he'd have to tell her, but only when their father would return from work. He didn't want to talk it all through multiple times. For now, he was going to just enjoy his cookies.

/break\

Luke smiled as he kissed his wife hello, their youngest daughter on his arm. Madzie was clinging onto him, talking animatedly about baking cookies with Clary. Clary was helping Catarina with dinner, both smiling and adding pieces to Madzie's story every now and again. The odd one out was Sebastian, who was staring blankly out of the window.

"That sounds like you were having a lot of fun, girls", noted Luke fondly.

He put Madzie down so he could set the desk, exchanging a questioning look with Catarina. His wife just shook her head with a small shrug. Apparently, she didn't know what was wrong with Sebastian either. Clary simply shrugged too as she went to put a plate in front of Sebastian.

"Dunno what's wrong with him. He's been spacing out all day", stated Clary airily. "Right, Seb?"

"Mh...?", grunted Sebastian, blinking slowly.

Concerned, Catarina stepped up to him. "Are you feeling alright, honey? Are you getting sick? Last weekend at Comic Con, did you catch something...?"

"No. I'm fine", mumbled Sebastian, ducking her.

"Something's bothering you, kiddo", noted Luke with two raised eyebrows.

The rest of the family joined them at the table as they started eating dinner. Sebastian poked the potatoes on his plate while he was trying to find the right words to tell them.

"When we were at Comic Con, I ran into an old... acquaintance?", offered Sebastian.

"Jace Herondale!", exclaimed Clary and nodded wildly. "Me and Simon saw the picture he posted of the two of you. It was like a super nostalgic reunion."

"He was your co-star in _Adventures of New Rome_ , right?", asked Catarina with a small smile. "You two used to be friends, didn't you...?"

"I... maybe, a little", offered Sebastian reluctantly. "Honestly, I got along best with Isabelle – who played Reyna. The two of us were... best friends, I guess. We even stayed in contact for a while after the show wrapped, but... well."

"So, it was nice to run into your old friend, then? Or... did it remind you...", started Luke.

Sebastian shook his head quickly. They tried to steer clear of things that might remind Sebastian of his abusive childhood. He sighed softly and put his fork out.

"Clary's not the only one who got nostalgic about it", continued Sebastian. "The internet freaked out about it. Turns out that with ten years since the finale, those who grew up on the show are now in a nostalgic age and seeing Jace and me together made them all hyped about it. The show trended again and was apparently rewatched a lot on Netflix..."

"How do you know that?", asked Catarina curiously.

"I... got a letter from Disney", offered Sebastian with a frown. "The great demand for it apparently gave them an... idea. Since neither show ever actually got into the sequel-books and there is no definite need for those to take place _directly_ after the first..."

"Wait. They want you to return to the show?", asked Clary a little confused.

"In a way", shrugged Sebastian. _Percy Jackson and the Olympians_ and _Adventures of New Rome_ both ended. This one is... a sequel to both. One show. A new show. From the elevator pitch, it sounds like... like a soft-reboot, in a way. It pulls you back into the show, with characters you know and loves from the original shows, but considering the plot is its closed, own thing, it perfectly works for new viewers without knowledge of the old?"

"And they want you to return in your role?", asked Luke, looking concerned.

"In the books, technically, there's ten main characters. Four new ones and respectively three alumni from the original shows. I'm... one of them. They say if they can get all six to sign on, they'd continue on developing the show", replied Sebastian. "Isabelle, Jonathan and I were the three leads from _Adventures of New Rome_. It... would be nice, to reunite with them. And a part of me has always regretted that we never really wrapped up the story."

"So, do you want to return to acting?", wanted Luke to know.

"I... have to admit, I've been thinking about it", answered Sebastian honestly. "And... ever since I finished high school, I've been... drifting around. I just don't know what I want from life... This, I was good at it, I enjoyed it. I do not regret stopping, I'm glad I got to experience what being a teenager was actually supposed to be, but... the chance to return to it..."

"If it's what you want, we'll support you", assured Luke, resting a hand on Sebastian's shoulder.

"Ye—es. I wanna see Sebbie acting acting!", exclaimed Madzie excitedly. "So I can brag to all my friends! None know the show he was in because we were all not born then!"

Sebastian choked on his laughter at that and reached out to ruffle his little sister's hair. He actually wanted that. Playing Octavian had been a lot of fun, he remembered the time he spent with Isabelle and Jonatha—Jace. Not to mention, back when he had read the books to prepare for the role, he really had wondered about the timeline. A massive war, prophecied for two thousand years... and the _next_ massive, prophecied war happening just half a year after? It was unnecessarily rushed to keep the main characters still 'relatable teenagers', Sebastian guessed. Personally, he would actually prefer this take on them, returning to being heroes, after ten years of peace. He would really enjoy returning to that role and he would also enjoy seeing Isabelle and Jace again.

/break\

"Wo—ow", hummed Simon in awe, eyes large.

"Mh?", grunted Clary as she continued doing her homework on the floor.

College was so much worse than high school. But she didn't want to miss time with her boyfriend. He was laying sprawled out on the couch, on his phone, one hand hanging over the couch and absentmindedly playing with her curls.

"Considering they got the main cast from _Percy Jackson and the Olympians_ and _Adventures of New Rome_ all signed on for the series, they started casting the last four big characters", rambled Simon and sat up. "And they just announced casting for Hazel Levesque and Leo Valdez."

"Well, who did they cast?", asked Clary, looking at her boyfriend.

"Maia Roberts and Bat Velasquez. This is super not good for my shipping", stated Simon with a serious frown. "They are like the cutest it-couple right now, how could I not ship their characters then...? But this show is getting better with every news we get!"

Clary raised her eyebrows and nodded slowly. Maia Roberts was a great actress, she had stared in a witch-comedy on Disney channel five years ago. It figured Disney would reign in some alumni. She just hoped that her brother would get along with them and that... that this would be a positive experience for him. That acting really was what he wanted.

/break\

Sebastian was gritting his teeth as he paced his dressing room. He hadn't acted in ten years and somehow, it seemed, he had gone a little rusty. It agitated him quite a lot.

"Take a deep breath, concentrate", offered Isabelle gently.

She sat cross-legged on the couch, with her own script in her hand. Sebastian paused his pacing for a moment of appreciation. The tall teen had grown into a beautiful young woman, who could still rock a toga. It was frighteningly easy to slip back into how things used to be, once upon a time. Back when he had still been Sebastian Verlac, raised by Valentine's agents to be the perfect little child-actor to make lots and lots of money. Only that now things were different. Now, Sebastian knew what love was. What being loved meant. Having loving parents and siblings. Now, acting was _his choice_ , not a choice made for him, a thing he would be punished for failing at.

"I suppose it's just... so different", sighed Sebastian and sat down next to her.

"You... don't have to if you don't want to", offered Isabelle, resting a hand on his thigh. "Your... Your new parents, they're... not _making_ you return to acting, right?"

Sebastian smiled faintly at her concern. She had been the one to notice that something had been wrong with Jace, she and her brother and they had led to the discovery of what Valentine was up to.

"My parents are... great", offered Sebastian reluctantly.

"Yeah? You were so weary the last time we spoke... oh, it's been so long", sighed Izzy in guilt.

"You and your family moved to Europe, your parents were in the middle of a divorce, your brother's coming out went more spectacular than anticipated... you had a lot on your plate too", counted Sebastian and shook his head. "It's okay. We were young, we had our own lives."

"So... tell me about them now?", prompted Isabelle curiously, tilting her head.

"Luke, he was... he was very awkward at first. I think he felt guilty that I never got to meet my birth-mother. Then, he got even more awkward when he started dating. Catarina, she's a nurse he met during a case. She is an amazing, head-strong woman", started Sebastian and leaned back some. "And Clary and I... she was like a wide-eyed puppy trailing after me when we first met, but we've grown closer since then. We trust each other. She makes horrible life-choices – like dating a musician nerd disaster – but I love her... a lot. My parents adopted an orphaned girl from one of Luke's cases, her name is Madzie and she's an absolute sunshine. Wait."

He got his phone out to show Isabelle his lock-screen – a picture of himself with Clary and Madzie. Isabelle cooed at the cute picture before launching into how she and Alec had been doing. It honestly helped him relax. It distracted him from the nerves, helped make things feel as natural as they had once upon a time. He smiled as he listened to Isabelle.

/break\

"He is unfa—airly sexy", muttered Jace with a pout.

"He's wearing a bed-sheet", countered Maia, one eyebrow raised in judgment.

"It's called a toga. And it looks sexy on him", grumbled Jace.

"He gutted a panda pillow pet earlier. And he looked like he _enjoyed_ it", argued Bat disturbed. "Like, not just that he was very in character, I think he personally enjoyed it."

"You're both buzz-kills", huffed Jace, waving his arms around. "He's gotten insanely sexy."

"Then just... visit his changing room after filming, shag it out and be done", sighed Maia. "There were so many variables that could have tanked this show before it took off, but drama due to UST is definitely not what should cost me this job and this chance of playing my favorite book-character."

Jace rolled his eyes at her. Over the past weeks of filming, he had befriended Maia and Bat in particular, though he got along with pretty much the whole cast.

There was just one _tiny_ problem. Or rather, well, something that used to be a tiny problem and was now slowly growing. Also known as Jace's crush on Sebastian Verlac-now-Garroway. He used to have a crush on the lanky teen back in the day already, with the pretty British accent and intense eyes and snarky nature. But now? He had filled out nicely and there was now a certain... gentleness that probably came from whatever normal, proper family had gotten to raise him in the past ten years. Jace smiled faintly to himself. He was glad Sebastian got a loving family.

"You're making heart-eyes again. Stop it, Herondale", grunted Maia and elbowed him.

"Says the girl cuddling her boyfriend at set", snorted Jace pointedly.

Maia didn't reply, just wrap an arm around Bat's shoulders and pull him in to kiss his cheek. Honestly, their real-life relationship really helped with the chemistry on account of Bat's character having a huge crush on Maia's. His pining puppy-dog eyes were _very_ real.

"Though honestly, some office romance here would totally get the show even more hyped?", offered Bat thoughtfully, with the smallest grin. "Everyone knows you're one of the most wanted bachelors around these days, Mister Herondale. Being snatched off the market in such a way? A true Hollywood romance. You should totally go for it."

"Don't encourage him", chided Maia, earning a kiss to the temple.

"You encouraged him first", countered Bat teasingly, arms around her waist.

"To shag, not to bag", argued Maia. "If they just fuck it out, get it out of their system, that's one thing. But romance can always go South..."

"I mean, they play enemies. Romance going South wouldn't affect that", shrugged Maia.

"You're both horrible people", declared Jace frustrated and got up.

He looked at the scene being filmed one last time before returning to his camper. Seb _was_ hot.

/break\

Sebastian was thoroughly enjoying the company of Lydia Branwell, who had played the female lead in the _Percy Jackson_ series. The two of them had never played alongside each other before, but Isabelle had, in the brief time she had cameoed in the original show. The two girls had gotten along really well back then and that friendship had only grown. Sebastian was happy to be a part of that.

"You've been staring at Jace a lot lately", pointed Lydia out casually.

"He's delightful to stare at", offered Sebastian equally casually. "Have you seen him in those skinny-jeans they put him in? An _utter_ delight, really."

Isabelle sputtered at that and shook her head in amusement. Sebastian was very open about his interest in Jace, yet he still refused to actually approach the other blonde. Isabelle was _very_ frustrated with them both. Locking eyes with Lydia, Isabelle smiled and nodded after checking her phone. Understanding, Lydia got up and offered Sebastian a smile.

"Well then, while you enjoy a little afternoon delight, Isabelle and I have to rehearse a scene."

Sebastian frowned confused and opened his mouth, but then the girls had already left his trailer. Moments later and Jace entered the trailer, with that typical bright smile. It lit up his mismatched eyes in a way that made the breath catch in Sebastian's throat in a very unwelcomed way.

"Hey, Iz texted me and said you wanted to go over our scene?", asked Jace.

Sebastian lifted a finger and walked past Jace to check the door. Yes. It did not open. He sighed. Isabelle Lightwood was the bane of his existence. His eyes widened when he noticed just how close Jace stood next to him. Sebastian could see the exact way in which blue and hazel met in those beautiful eyes. Sebastian shook his head. Not the moment to think those thoughts.

"Wait. Did... Iz and Lyd lock us... in?", asked Jace slowly, frowning.

"Yes. They have", sighed Sebastian and sat down.

Jace's eyes widened and his cheeks colored. Isabelle knew about his crush on Sebastian. He had gushed to her first, back after Comic Con when he had gotten to take a picture with Seb. How Seb was the main reason why Jace had wanted in on the sequel show, considering he was a movie-star by now and returning to TV was a bit of a step back. He didn't regret it though, beyond the bonus of seeing Sebastian again. Being on set with Isabelle again, making new friends here. The set of a show was always far more like... family, for how long it lasted.

"I'm sorry", blurted Jace out, running his fingers through his hair.

" _You_ are sorry?", asked Sebastian mildly confused.

"Maia and Bat have been hounding me for weeks and I guess Iz has grown tired of me too", mumbled Jace, burying his face in his hands. "I kind of... like you. A lot."

"I'm sorry, what?", asked Sebastian, eyebrows raised.

Removing his hands just enough to peek out and look at Sebastian, Jace repeated. "I like you."

"Ah. Uh. That... was unexpected", grunted Sebastian and straightened his shirt.

"I... figure", sighed Jace. "Right. This was fun."

"No. Wait", ordered Sebastian and caught Jace by the arm. "It's unexpected because the reason for Isabelle's little games here is that she is well-aware of my... feelings for you."

"Say that again", requested Jace, staring at Sebastian like he grew a second head.

"I like you too", offered Sebastian, slipping his hand up to cup Jace's cheek.

The other blonde instinctively leaned into the touch, causing Sebastian's heart to make off things again. He couldn't help but lean in too, closer and closer until he could count the lashes surrounding Jace's pretty eyes. And then, he got to experience what Jace's lips felt like against his. They were soft. So very soft. They felt rather perfect against his own. So did all of Jace though, leaning heavily against Sebastian's chest, resting a hand against it for support as he stood just slightly on his toe-tips. His other hand was resting in the nape of Sebastian's neck. Urged forward by Jace like that, Sebastian wrapped his own arms around Jace's waist to hold him close.

"On whoever's behalf they have done it, I think it benefited us both", whispered Sebastian.

"...Yeah", whispered Jace, nodding slowly. "Yeah."

"So eloquent", teased Sebastian amused. "Don't tell me a little kissing messes with you like that. I can't wait to see just how much _other_ things will mess with you."

The blush on Jace's cheeks was absolutely _delightful_. This show was _exactly_ what he had needed.

 _~*~ The End ~*~_

* * *

 _Author's note: When I got this title during the Fake Fic Title game on tumblr (come visit me at **takaraphoenix** before tumblr completely implodes ;D), I HAD to go SebJace actors AU. And I felt like I was being hit by a car when I realized Jace = Jason and Sebastian = Octavian would be peeerfect choices. Also, I now want that exact TV show, like dear PJatO readers imagine a TV show diving more into the Romans. Hng. Anyway, I hope you enjoyed the fic! ^o^_


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